Describes pathology of the combined tendon of the gastro-soleus complex, which inserts onto the calcaneum.

Three stages of injury:

Paratenonitis.

Tendonosis with or without paratenonitis.

Rupture – partial or full. A complete tear may be acute or chronic, sometimes with no prior symptoms.

Clinical features

Relate to the stage of the injury:

Localised tenderness proximal to the insertion, and crepitus on ankle movement.

Tendonosis Nodular thickening and degenerative change within the tendon presents as focal thickening within the tendon, which is only tender in the presence of paratenonitis.

Rupture – classically a middle-aged patient (M>F) who undergoes a sudden, forceful contraction of gastro-soleus during infrequently performed sporting activity – ‘I thought I was kicked in the back of the leg’. The classic gap may not be palpable, but Simmonds Test will be abnormal in the vast majority of ruptures (>95%).

Radiological features

USS and MRI can be used in the diagnosis of all three stages of Achilles tendonopathy.

USS:

Normal tendon

uniform thickness<7 mm.

Tendonosis

fusiform swelling.

heterogeneous echo pattern.

hypoechoic foci (mucoid degeneration).

In an acute full-thickness tear, in the presence of good clinical signs there is no need for imaging; if there is doubt over partial continuity, then both USS and MRI are diagnostic.